This invention relates generally to a rotary expansion steam power unit of the type having a planetating rotor, and more particularly, to an improvement in the means for providing the expansion fluid to the expansion chambers in such a unit. Such improvement includes, among other things, means for isolating the main shaft and working bearings of the engine from such hot expansion fluid.
Rotary expansion engines of the type having a housing defining a plurality of epitrochoidal cavities, a rotor element movable within said cavities, and eccentric means including a crank shaft on which the rotor rotates are well known in the art. These engines also include appropriate seals and valving means for selectively directing expansion fluid into the plurality of expansion chambers defined by the engine hosuing and the outer surfaces of the rotor. A typical rotary expansion engine of this type is described in Hoffmann U.S. Pat. No. 4,047,856.
In rotary expansion engines generally, including the engine described in U.S. Pat. No. 4,047,856, it has been found that the interior of the rotor member provides a convenient inventory for the expansion fluid. This expansion fluid is then selectively released to the respective expansion chambers by various valve means. As an example, the expansion fluid may be released into the respective expansion chambers by passage of the rotor circular side seals over various contoured valving cavities positioned in the end walls of the engine housing. In constructions such as this, the rotor journal bearing is surrounded with hot expansion fluid such as steam. This requires such bearings to be provided with an otherwise excessive flow of cooling oil necessary to keep the bearing from failing due to excessive heat. Also, when the hot expansion fluid is allowed to enter the interior of the rotor, the rotor attains high heat due to its being internally bathed in the hot expansion fluid, thus leading to excessive expansion and loss of dimensional control.
Thus, there is a need for a rotary expansion engine having means for isolating the hot expansion fluid from the main shaft, the shaft support bearings and the phasing gears and for providing lubrication and cooling oil thereto.